Marbled Sugar Cookies

In a large bowl, using an electric mixer on medium-high, cream butter and sugar until fluffy. Add yolk and vanilla, then beat until incorporated. Add flour and salt; mix on low speed until dough forms a ball.

Divide dough into 5 balls. On a lightly floured piece of parchment, add a few drops of food coloring to 1 dough ball. Knead until color is evenly distributed. Repeat on fresh parchment with remaining dough and colors.

Divide each dough ball in half. Combine each half with another color, pressing halves together. Tear a 2-color dough ball into pieces, and press back together several times (to create marbled effect). Repeat with remaining 2-color dough balls. Press each marbled ball into a disk, wrap in plastic and refrigerate until firm, about 30 minutes.

Preheat oven to 375°F. Line a baking sheet with parchment. Remove 1 dough disk from refrigerator. On a well-floured surface, roll dough to 1/8-inch thickness. Cut with leaf-shape cutter. Place cookies 1 inch apart on baking sheet. Use dull side of a paring knife to press veins onto leaves. Wrap and refrigerate scraps.

Bake cookies until firm, 8 to 12 minutes. Slide entire parchment sheet with cookies onto a wire rack; allow to cool completely. Repeat with remaining dough and chilled scraps, using fresh parchment and combining scraps to create multicolored leaves.